Pavlovian conditioning plays an important role in several aspects of drug abuse and addiction, yet its contribution to the initiation and pre- addictive development of drug use is largely unknown. We have found that very low doses of ethanol, which have few effects on instrumental learning or spontaneous behavior, can facilitate Pavlovian conditioning, coupled with its generality across species, situations and behaviors, raises important questions regarding whether other abused, depressant drugs might exert similar facilitatory effects at comparably low doses. Opiates, benzodiazepines and barbiturates share with ethanol low-dose, stimulant- like effects which might also enhance Pavlovian conditioning. Since initial drug self-administrations are generally at low doses, such an effect could exert strong influence in determining the sequelae of initial or occasional drug use, depending on appetitive or aversive Pavlovian contingencies present in the situation. Preliminary data suggest that prototype drugs of these classes do, indeed, influence Pavlovian conditioning at very low doses and that some of these effects are facilitatory. Since low-dose effects of abused drugs on Pavlovian conditioning are largely unstudied, and since appetitive conditioning, in particular, may be important to motivational factors predisposing to the acquisition of drug abuse, we propose to a) determine the effects of low doses of prototype opiate, benzodiazepine and barbiturate drugs on appetitive Pavlovian conditioning; b) compare these effects to those on aversive conditioning and pseudoconditioning; and c) determine whether facilitatory drug effects on appetitive Pavlovian conditioning are paralleled by enhancement of the ability of a Pavlovian conditioned reinforcer to establish operant behavior. Conditioned changes in ergometric activity and bar-pressing of rats will be used as a test system. Our work suggests that this should be a sensitive and efficient model for conducting the proposed studies, as well as subsequent studies pursuing the long-term goal of understanding how low-dose effects of drugs on Pavlovian conditioning might influence subsequent self-administration of those drugs.